THIS INVENTION relates to a strain/electrical potential transducer. It relates to generating displacement by means of converse piezoelectric effect or electrostriction. It relates more specifically to a displacement generator, to a manipulating device and to a microscanning device. It relates also to sensing displacement by means of direct piezoelectric effect.
The Applicant believes that one species of this invention can particularly advantageously be worked by means of converse piezoelectric effect, and that application will predominantly be borne in mind for purposes of this specification. However, the Applicant does not wish to exclude similar ways of obtaining small displacement by applying a changing electrical potential to a dielectric material, such as electrostriction, and such applications, where appropriate, are included within the scope of this invention. For convenience, the phrase xe2x80x9celectro-deformation of dielectric substancexe2x80x9d or similar phrases, will to a limited extent be used in this specification and the phrase is or the phrases are to be interpreted to denote converse piezoelectric effect, electrostriction and similar phenomena.
Furthermore, in another species of this invention a transducer is used as a sensor by making use of direct piezoelectric effect. By subjecting the transducer to displacement under force causing stress, electrical potential is generated signalling the presence of stress and thus displacement under force. As a variant, in so far as strain relates to stress or force, the transducer can be used to sense stress or force. Sensing stress or force will be regarded, for purposes of this specification, as equivalent to sensing displacement. Such applications fall within the scope of this invention, and this specification covers also such xe2x80x9creversexe2x80x9d applications.
In accordance with a first aspect of this invention, there is provided a strain/electrical potential transducer including
a rigid base,
an elongate stack of dielectric substance having electrical contactors arranged to be subjected to an electric potential associated with electro-deformation of the dielectric substance, a first end of the elongate stack being hinged to the base at a stack hinge position;
a rigid beam hinged at a first end thereof to the base at a beam hinge position, the rigid beam being transversely spaced from the elongate stack and extending generally longitudinally with the elongate stack;
a rigid connecting link extending transversely between and interconnecting opposed ends respectively of the elongate stack opposite to said first, hinged end, and of the rigid beam opposite to said first, hinged end, the configuration being such that longitudinal deformation in the elongate stack and transverse displacement in said opposed end of the rigid beam are causally connected.
The elongate stack may preferably be of piezoelectric material.
The transducer may be arranged in a plane.
Hinging may advantageously be by means of solid hinge formations allowing hinging. The solid hinge formations may be of a material having high fatigue strength, such as titanium.
Instead, the hinges may be articulated. They may, for example, use ball joints, however, it is regarded as important that the hinges should provide no or very little lost motion.
Preferably, connection of the rigid connecting link to respectively the elongate stock and the rigid beam is with no lost motion.
By way of development, the transducer may be of composite structure, said elongate stack and said rigid connecting link being respectively a first elongate stack and a first connecting link, the transducer including also a second elongate stack and a second rigid connecting link arranged in a fashion similar to and connected in a fashion similar to the first elongate stack and the first connecting link; Thus the transducer may include a first sub-arrangement comprising the first elongate stack and the first rigid connecting link, and a second sub-arrangement comprising the second elongate stack and the second rigid connecting link, the first and second sub-arrangements being symmetric and sharing the rigid beam which is common to the first and second sub-arrangements. The sub-arrangements may be mirror images.
Advantageously, the rigid beam may be placed under tension to compress the first and second elongate stacks, such that, in use, tension in the elongate stacks is obviated or at least limited. Thus, the elongate stacks will operate in compression or mostly in compression.
In one species of embodiment, the transducer may be in the form of a displacement generator. Then, the or each elongate stack may be a piezoelectric material adapted to produce a converse piezoelectric effect.
In another species of embodiment, the transducer may be in the form of a displacement sensor. The or each elongate stack may be a piezoelectric material adapter to produce direct piezoelectric effect.
The invention extends to a composite strain/electrical potential transducer comprising a plurality of transducers which are combined to have a single displacement input/output and a single electrical potential input/output.
In accordance with a second aspect of this invention, there is provided a manipulating device for use in an optical system, the manipulating device including
a frame for holding an optical element;
a plurality of transducers in the form of displacement generators as herein described and which are operatively connected to the frame and having connecting means for operative connection to an anchor member such as selectively to generate displacement of the frame relative to the anchor member.
Bases of the respective displacement generators may be connected to the anchor member. In practice, the anchor member may form bases for the displacement generators, the second end of the rigid beam of each displacement generator being connected to the frame.
The displacement generators may be arranged symmetrically. They may advantageously be two, three or four in number. They may be arranged in a plane.
The frame may be round, the displacement generators extending radially outwardly from the frame.
The displacement generators may be arranged such that said relative displacement between the frame and each displacement generator is in a longitudinal direction relative to an axis of the optical element to be held in the frame.
In a preferred embodiment, the displacement generators may be even in number and may be arranged in opposed pairs, the displacement generators in each opposed pair being in the same orientation and in opposite orientation to another opposed pair, the displacement generators being prestressed to cause the displacement generators to operate in compression or at least mostly in compression, the prestressing load in one pair of displacement generators being balanced by the prestressing load in the other pair of displacement generators, the prestressing loads being transmitted to the frame, the frame or the frame in combination with the optical element when in position, then being rigid such as to balance the prestressing loads.
The second aspect of this invention extends to a combination of a manipulating device as herein described in combination with a generator of electrical potential which is controllable selectively to generate fluctuating potential difference to drive the stacks. The generator of electrical potential may be a solid state generator having a plurality of outputs corresponding to the plurality of displacement generators or pairs of displacement generators, the combination including software or logic to manage or control the generator of electrical potential.
The invention extends in respect of a third aspect to a microscanning device including an optical receiver, an optical system directed at the optical receiver and a manipulating de/ice as herein described and in which an optical element is held in the frame to form part of the optical system, the manipulating device being operable selectively and fluctuatingly to refract optical beams projected via the optical system to effect microscanning.